1. Field of the Invention
The present invention relates to a ceramic heater and, for example, to a ceramic heater-used in a ceramic glow plug or the like.
2. Description of the Related Art
Conventionally, as a ceramic heater used in a ceramic glow plug or the like, there has been known a ceramic heater in which a ceramic resistive heating element containing WC as a main component is embedded. in an electrically insulating ceramic body containing Si.sub.3 N.sub.4 or the like as a main component.
In the aforementioned ceramic heater, because the thermal expansion coefficient of Si.sub.3 N.sub.4 constituting the ceramic body is smaller than that of WC which is a main component of the resistive heating element, concentration of stress based on the difference between the thermal expansion coefficients may occur in the resistive heating element to bring a problem in the durability of the resistive heating element when a cycle of heating and cooling is repeated.